1. Field of the Invention
The present invention relates generally to tissue treatment systems and in particular to use of nucleic acids with reduced pressure therapy for the treatment of wounds.
2. Description of Related Art
Clinical studies and practice have shown that providing a reduced pressure in proximity to a tissue site augments and accelerates the growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but application of reduced pressure has been particularly successful in treating wounds. This treatment (frequently referred to in the medical community as “negative pressure wound therapy,” “reduced pressure therapy,” “subatmospheric pressure therapy,” “vacuum sealing therapy” or “vacuum therapy”) provides a number of benefits, including faster healing and increased formulation of granulation tissue. Typically, reduced pressure is applied to tissue through a porous pad or other manifolding device. The porous pad contains pores (also called “cells”) that are capable of distributing reduced pressure to the tissue and channeling fluids that are drawn from the tissue. The porous pad often is incorporated into a dressing having other components that facilitate treatment.
Wound healing may be broadly split into three overlapping basic phases: inflammation, proliferation, and maturation. The inflammatory phase is characterized by hemostasis and inflammation. The next phase consists mainly of epithelialization, angiogenesis, granulation tissue formation, and collagen deposition. The final phase includes maturation and remodeling. The complexity of the three step wound healing process is augmented by the influence of local factors such as ischemia, edema, and infection, as well as systemic factors such as diabetes, age, hypothyroidism, malnutrition, and obesity. The rate limiting step of wound healing, however, is often angiogenesis. Wound angiogenesis is marked by endothelial cell migration and capillary formation where the sprouting of capillaries into the wound bed is critical to support the regenerating tissue. The granulation phase and tissue deposition require nutrients supplied by the capillaries. Impairments in wound angiogenesis therefore may lead to chronic problem wounds.
Expression of the angiogenic phenotype is a complex process that requires a number of cellular and molecular events to occur in sequential steps. Some of these activities include endothelial cell proliferation, degradation of surrounding basement membrane, migration of endothelial cells through the connective tissue stroma, formation of tube-like structures, and maturation of endothelial-lined tubes into new blood vessels. Angiogenesis is controlled by positive and negative regulators. In addition to endothelial cells, cells associated with tissue repair, such as platelets, monocytes, and macrophages, release angiogenic growth factors such as vascular endothelial growth factor (VEGF) into injured sites that initiate angiogenesis.
There are currently several methods used to augment wound healing, including irrigating the wound to remove toxins and bacteria, local and systemic administration of antibiotics and anesthetics, and local application of growth factors. One of the most successful ways to promote wound healing in soft tissue wounds that are slow to heal or non-healing is reduced pressure therapy, discussed above.
Although reduced pressure therapy is highly successful in the promotion of wound healing, healing wounds that were previously thought largely untreatable remains difficult. Because the inflammatory process is very unique to the individual, even addition of reduced pressure therapy may not result in a fast enough response for adequate healing. Thus, the wound healing process can be very slow and laborious, which can be inconvenient to the patient and sometimes costly. Thus, it is desirable to find ways to augment reduced pressure therapy to decrease the time that reduced pressure therapy is needed.